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The YZ Linear Regulated Power Supply is an easy to assemble, all-in-one power supply solution for audio amplifiers such as the Audinst HUD-MX1. The design borrows heavily from various other LRPS designs such as the σ25 from AMB but is meant to provide a slightly more integrated solution along with moderately better performance.

The YZ LRPS utilizes a TO-220 form factor positive fixed linear regulator such as the LM340 or LM7815 series and takes an input voltage of up to 35Vpeak from a wall transformer based on the regulator used. (Note that for a negative output you’d have to switch the + and – output of the bridge rectifier chip) The fuse, switch wirepads, and all of the linear power supply circuitry is integrated on one board – it is meant to be used inside of a HAMMOND project enclosure and all it needs is reduced VAC from a wall transformer of your choice to function. DO NOT connect this directly to the 115VAC from your wall outlet, as you will simply fry pretty much everything on the board with the high voltage! Alternatively you could use it with an unregulated DC power supply and omit CSH and the bridge rectifier.

Theory of OperationA reduced VAC (say 16VAC) comes in from your wall transformer to the board. CSH shunts away high frequency line noise and transients. Five fairly large input filter capacitors are used along with the bridge rectifier to provide an excellent filtering stage. At this point you essentially have a fairly good unregulated DC signal. A bleeder resistor (R2) is implemented in order to provide a discharge path for the capacitors when the power supply is turned off for safety purposes.

CBY bypasses the input to the voltage regulator IC and helps reduce input ripple. A 1N4002 diode is implemented as a protection diode for the regulator IC. Electrolytic, tantalum, and ceramic capacitors (C5, C6, C7) are paralleled at the output of the regulator in order to provide excellent transient performance and extremely low impedance over the entire high frequency range. This was an idea I got from Application Report SLTA055 by TI.

Input/output voltages and your on/off switch are hooked up by terminal blocks which accept between 26-16AWG. I find that these work fairly well and provide an easy means of wiring stuff to the PCB. I considered using Molex connectors as well but I honestly don’t think they are particularly useful here. Since this power supply can technically handle 1A of max current I’d recommend using at least 22AWG thick wire throughout the build – I’ve used fairly thick traces to account for this on the PCB as well. A fairly large ground plane is implemented in order to reduce noise and minimize stray inductance among other benefits.

Note that I’m building a 15V power supply specifically for the Audinst HUD-MX1, but only slightly tweaks need to be made if you want different output voltages for other applications. Many of these parts are incredibly common and you can probably get cheap alternatives for almost everything from a vendor such as Tayda Electronics. You can do quite lot with the board and I encourage you to come up with your own customizations and part selections – this parts list is more or less here just to get your started.

Part

Qty

Mouser Part ##

Description

AC Adapters 120VAC to 16VAC 1.0A

1

553-WAU16-1000

Wall transformer from TRIAD Magnetics that dumbs the AC line voltage down to 16VAC; excellent build quality but rather large

ACIN/DCOUT/SW – Fixed Terminal Blocks 2P LS5.08mm 90DEG

3

651-1729128

Hardy little terminal blocks from Phoenix Contact that I use for hooking up wires to the PCB – you could alternatively solder everything directly to the PCB but then if anything goes wrong have fun with that…

DCOUT – DC Power Connector 2.1mm Pwr Plug Red Tip Blk Handle

1

502-762

Very high quality 2.1mm ID / 5.5mm OD DC power connector from Switchcraft – very expensive but I still like it a lotI’m not sure why DC power connectors cost so much off of Mouser but they are good quality connectors

Just little grommets you fill holes in your enclosure with to pass wires through; choose your own from the Mouser mounting hardware section

F1 Fuseholder for 5x20mm fuses

1

576-65600001009

Just the fuseholder for a standard 5x20mm fuse – you could short this and not use a fuse at all but I wouldn’t recommend this – I’ve already blown one myself while testing this thing

F1 Fuseholder Cover (optional)

1

576-66000001009

This is a little cover for the fuse holder if you feel like being neat – not at all necessary

F1 5x20mm 1A Fast-Acting Fuse

1

576-0217001.MXP

This guy will blow immediately if more than 1A of current passes through it, which is probably what we want since most of the parts in this list can only take that much current

SW – any panel mount switch from Mouser or Radio Shack

1

Find your own

Mouser carries a huge selection of switches; Radio Shack has a good selection as well and you can choose one that you think looks cool (make sure your switch can handle line voltages)Since the board is fairly small you should have quite a lot of space inside your enclosure to work with so switch dimensions shouldn’t be an issue for the most part

Resistor to set LED operating current which will depend on your desired output voltage and LED – you can easily calculate this with one of the many LED resistor calculators available online [http://ledz.com/?p=zz.led.resistor.calculator]For my 15V power supply and the LED in this parts list this yields about 17mA of current through the LED which I find is decently bright.

LED – Standard LED – Through Hole Blue Round LED

1

941-C503BBCSCV0Z0461

LED from Cree that has a 3.2V typical forward voltage and a desired operating current of around 20mAYou can be lazy and just drill a hole through the enclosure for the light to shine through or you can use an actual LED panel mount (Mouser #749-CR-174)

Project Enclosure (HAMMOND)

1

546-1591XXSSBK

The specific project enclosure that this PCB is designed to fit in – measures 4.3L x 3.2W x 1.6HYou only use two #4 screws to mount one side of the PCB down onto the enclosureIf you want to use another enclosure you can always drill mounting holes of your own into the PCB or just use some sort of adhesive on the backside

*Project Enclosure (Alt)(HAMMOND)

1

546-1591XXTSBK

A possible alternate enclosure if the recommended one is out of stock – measures 4.8L x 3.2W x 2.2HYou’ll need to re-drill two holes to mount the PCB inside this one

PCB Screws for Project Enclosures

1

546-1593ATS50

#4 self-tapping screws that HAMMOND makes for screwing down PCBs in its enclosures; you could simply go to a local hardware store and buy a couple as well since these are standard screws anyway

Notice that I believe in putting my money where it counts so I don’t go around suggesting overkill parts for your build – my Lelon input filter capacitors and AVX tantalum cap really won’t perform any worse in this circuit than Nichicon and Kemet caps. Things like heatshrink, wire, and solder I expect you to find by yourself or just have laying around. For solder I usually use Cardas quad (can be found on eBay) or 62/36/2 from RadioShack. Heatshrink and wire I usually just buy in bulk off of eBay or Tayda Electronics.

AssemblyAll parts on this board are through-hole and fairly well spaced so that even those new to soldering can assemble this project with relative ease. The design still manages to remain reasonably compact with overall board dimensions of 2.5″L x 2.0625″W. You’ll end up with quite a bit of free space inside the HAMMOND enclosure to work with.

The parts in my recommended parts list are for a 15V power supply for the Audinst HUD-MX1 audio amplifier – if you need a different output voltage you can use your own parts as necessary. You can pretty much build a power supply for any fixed TO-220 linear regulator that you can find on the market – just make sure you are familiar with the design and know what you are doing before you go around using random parts of your own. I won’t take any responsibility for things getting blown up – I just provide the board and what you put on it is your own problem.

Safety Note: Be careful when working with live circuits as they can kill you! The discharge from the four filter caps is most definitely lethal, though implementation of the bleeder resistor does allow things to decay to safe levels fairly quickly. Always ask someone more experienced to help you if you are unsure about something.

PrototypeHas similar parts and topology to the full version that I plan on making so I’ve been testing it out. So far it seems to be working great without any issues. The green PCB you see in the picture is the Nightfire Electronics Kit #1772 with mostly parts from the parts list above. (I didn’t use anything included in their kit, though they actually include some pretty decent stuff) The separate board with the fuse and terminal blocks is a simple one layer PCB that I etched in my basement. The circuit board in this project is more or less a combination of the two boards in the picture with some more bells and whistles.

I tested this power supply vs the stock Audinst HUD-MX1 power supply by loading them to 200mA of output current and AC coupling the output to my true RMS benchtop DMM by means of a 0.47uF WIMA MKS cap and a 100K resistor. This way I could use the smallest 200mVAC range on my DMM to get an idea of the ripple voltages. I’ll try to follow up with better measurements sometime if I can get my hands on a decent oscilloscope. The stock Audinst HUD-MX1 switching power supply measured ~1mVrms which is not bad at all for a switching unit. (was getting some variation in the measurements) The switching frequency appears to be around 680KHz or so which is well above the audio range. My prototype LRPS measured 0.04mVrms (consistently) which is very good. The Audinst stock unit is actually not too bad as far as swtiching power supplies go, but for a bit of your time and money you can do quite a bit better and learn something in the process by building yourself a nice little LRPS like the one pictured above.

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MP3 is seriously outdated people…and so is NeroAACenc. There are better options out there now and keeping your audio in AAC-LC format at TVBR127 quality gives you excellent audio quality along with small filesizes. Lack of encoding utilities for doing this is somewhat of an issue…but you can have foobar2000 and QAAC encoding to AAC TVBR127 fairly quickly and painlessly.

You can access the foobar2000 converter by right clicking a song or songs within foobar2000 and going to Convert -> …

See screens below; foobar essentially decodes the file you’re converting to a temporary wave file and passes it to QAAC along with the custom commands you put in the “Parameters”

Convert!

I guess you could always keep your whole collection in FLAC as well if you have the space…but I think that TVBR 127 is the new best lossy audio format vs MP3 320KBps that a lot of people still seem to be using.

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IntroThis is a pretty short and simple project for me – as you might be able to guess from the title it’s essentially an adaption of the USB isolator by Circuits@Home except with the whole switching power supply section cut out and a LM340-5.0 based linear regulator section spliced in there instead. Full credit goes to Circuits@Home for an overall excellent design; I kept most of their board layout intact with only the power section changed. I intend for this thing to be used as a sort of isolator dongle for USB DAC headphone amplifiers; this will enable you to get clean 5V power from a linear regulator rather than from the PC USB bus. The design is kept very low profile with the use of mostly SMD parts and the board is overall slightly smaller than the original one by Circuits@Home.

Parts ListI won’t go into too much detail here as it is a relatively straightforward build and I encourage you to go out and find your own parts from the links to the side rather than just copying and pasting the part numbers I have written down below.

5V fixed SOT-223 form factor VREG. Ground plane of the board serves as a heatsink for this guy. You can get samples of these from National Semi or buy some from any of the big parts vendors Mouser Part #926-LM340MP-5.0/NOPB You could use another SOT-223 fixed 5V VREG in this position if you want but I believe that the LM340-5.0 is a very good part in general.

1N4001 Diode

1

Protection diode for VREG – you can find these guys pretty much anywhere. I have a bunch that I got for cheap from thaishopetc Mouser Part #512-1N4001

24Ω 1% tolerance 1206 SMD Resistor

4

I’m using Vishay CRCW120624R0FKEA from Mouser

1MΩ 1206 SMD Resistor

3

I’m using Vishay CRCW12061M00FKEA parts from Mouser

MLCC 0.1uF X7R 1206 SMD Capacitor

5

Bypass capacitors – a fairly common part that you can find around anywhere I’m using Vishay VJ1206Y104KXAMC parts from Mouser

MLCC 0.22uF X7R 1206 SMD Capacitor

1

Optional additional bypass for the VREG I’m using Vishay VJ1206Y224KXATW1BC parts from Mouser

MLCC 10uF X7R 1206 SMD Capacitor

3

Serves as a power reservoir for the circuit – would’ve been better to just use a bit electrolytic here but I wanted to keep things low profile I’m using Taiyo Yuden TMK316B7106KL-TD parts from Mouser

PWRLED – 1206 SMD LED

1

Pretty much any 1206 SMD LED will do; I have a bunch laying around from Sky-Electronic Mart Something like Mouser Part #696-SML-LX1206IC should work

RLED – 1206 SMD Resistor

1

Value depends on the specs of the LED you choose (will probably end up something like 150-220Ω) LED Calculator Link: http://ledz.com/?p=zz.led.resistor.calculator (supply voltage is 5V) I’m using a 180Ω Vishay CRCW1206180RFKEA parts bought from Mouser with my LEDs that have a FV of 2.2V and FC of 20mA.

Wall Wart Adapter

1

Needs a 2.1mm ID / 5.5mm OD plug which is fairly common It is critical that you use a power supply with center barrel positive, otherwise when you plug it into this board bad things will happen. I’m using the Triad Magnetics WDU75-800 which can be bought from Mouser

Assembly Basic assembly procedures are more or less the same as with Circuits@Home’s original design: http://www.circuitsathome.com/adum4160-usb-isolator-assembly-guide Those new to soldering may need a bit of help from someone more experienced or perhaps some extra practice with soldering down SMD parts. Those experienced with soldering should have no issues with the assembly except for potentially with soldering of the main USB isolator chip – alignment of this guy can be a bit tricky. All of the SMD resistors and capacitors are 1206 which is pretty large within the SMD realm so you should have no problems there; the SOT-223 VREG is fairly large as well so you should have no problems there. I’ll follow up with some basic images of the assembly for this particular board within a month or two.